Medically reviewed by Chandre Tina May, Registered Nurse & Menopause Society Certified Practitioner (MSCP). See our editorial policy.
You finally have a diagnosis. Someone looked inside your body, found the endometriosis, and then told you it was “mild” — Stage I or Stage II. And yet you’ve been doubling over every month, missing work, cancelling plans, lying on the bathroom floor. The word “mild” landed like a slap. If it’s mild, why does it feel like this? If you’ve been there, you are not exaggerating. Your pain is real, and the staging system is — genuinely — a poor measure of it.
This post will explain exactly what the four endometriosis stages do and don’t tell us, why “Stage I” can hurt as much as “Stage IV,” and what that means for how you seek care and talk to your doctors.
What Endometriosis Staging Actually Measures
Think of your pelvis as a house. The endometriosis staging system is essentially a surveyor’s report — it documents how much structural damage has been done: how many rooms are affected, whether the walls have cracked, whether the foundations are compromised. What it does not measure is how liveable the house feels to the person inside it. A small crack in a load-bearing wall can make the whole place feel unsafe. A large patch of damp in a spare room might go unnoticed for years.
The most widely used staging system is the revised American Society for Reproductive Medicine (rASRM) classification, which divides endometriosis into four stages based on what a surgeon sees and scores during laparoscopy:
- Stage I (Minimal): Small, superficial implants on pelvic organs or the peritoneum. Little or no scar tissue.
- Stage II (Mild): More implants, slightly deeper. Some minor adhesions may be present.
- Stage III (Moderate): Multiple deep implants, small endometriomas (cysts on the ovaries), and more significant adhesions.
- Stage IV (Severe): Extensive deep implants, large endometriomas, and dense adhesions — sometimes involving the bowel, bladder, or other structures.
The score is based on location, depth, and size of lesions, as well as the extent of adhesions. It is primarily a tool for assessing fertility impact and surgical complexity — not for measuring pain or quality of life. According to Endometriosis.org, the staging system was never designed as a pain-severity tool, and research consistently shows it performs poorly as one.
Why Stage and Pain Don’t Match Up
This is the part that confuses — and frustrates — so many women. If Stage IV is “severe,” shouldn’t Stage IV be the most painful? Often, no. And this is not a quirk. It’s a well-documented feature of how endometriosis behaves.
Location matters far more than size
A tiny implant sitting on or near a nerve — such as the uterosacral ligament, which sits close to nerve bundles — can cause agonising, radiating pain. A larger endometrioma on an ovary, if it isn’t pressing on anything sensitive, may cause far less day-to-day pain. The surveyor’s report measures square footage, not proximity to the fuse box.
Central sensitisation changes everything
In many women with endometriosis, especially those who have lived with pain for years, the nervous system itself becomes sensitised. This is called central sensitisation, and it means the brain and spinal cord amplify pain signals — sometimes long after the original source of inflammation has been treated. This is recognised in clinical guidelines including those from the National Institute for Health and Care Excellence (NICE) as a key driver of persistent pain that has no relationship to lesion size or stage.
Individual biology and inflammation vary
How your immune system responds to endometrial tissue outside the uterus, how much inflammation is produced, and how your own hormones interact with those lesions all vary enormously between women. Two women with identical staging scores can have completely different inflammatory responses — and completely different pain experiences.
The Problem With Being Told You’re “Only” Stage I or II
One of the most harmful things that happens in clinical practice is when a woman’s pain is minimised because her stage is low. “It’s only mild” becomes a reason to under-treat, to dismiss, to send her home with paracetamol and a gentle smile. This is a misuse of the staging system — and it delays appropriate care.
The NICE guideline on endometriosis is clear: pain should be assessed and treated based on its impact on the woman’s life, not on surgical staging. If your pain is disrupting your work, your relationships, your sleep, or your mental health, that is clinically significant regardless of what the laparoscopy found.
You deserve to have your pain taken seriously. If it isn’t, you are entitled to push back — and the section below on talking to your doctor gives you the words to do that.
What the Stages Can Usefully Tell You
The staging system isn’t worthless — it’s just being used for the wrong job when it’s applied to pain. Where it genuinely helps:
- Surgical planning: A Stage IV classification alerts a surgeon that the operation is complex, likely involving adhesions around the bowel or bladder, and may require a specialist team.
- Fertility conversations: Higher staging, particularly the presence of endometriomas or tubal damage, does have a relationship with fertility impact and informs discussions about fertility preservation or treatment.
- Monitoring progression: Repeated imaging or surgery can indicate whether the disease has advanced, which may influence treatment decisions.
Understanding what staging is for helps you ask better questions. If a doctor is using your stage to tell you how much pain you should be in, that’s the wrong question — and you can say so.
It’s also worth knowing that endometriosis is notoriously underdiagnosed, with women waiting an average of several years from first symptoms to confirmed diagnosis. If you haven’t yet been assessed, or if symptoms have changed significantly since your last laparoscopy, that matters. You can read more about how endometriosis is diagnosed and why it takes so long for a fuller picture of the diagnostic journey.
What Actually Helps — Managing Endometriosis at Any Stage
Treatment should be guided by your symptoms, your fertility goals, and your quality of life — not your staging number. Here’s what evidence supports:
Lifestyle approaches
- Anti-inflammatory nutrition: Some women find reducing highly processed foods, red meat, and alcohol — and increasing omega-3-rich foods — helps with inflammation. The evidence is still emerging, but it’s low-risk and worth exploring with a dietitian.
- Pelvic floor physiotherapy: Many women with endometriosis develop pelvic floor dysfunction as a secondary consequence of pain. A specialist pelvic physiotherapist can help release muscle tension and improve function.
- Pain psychology and mindfulness: Given the role of central sensitisation, approaches that work with the nervous system — including pain-focused cognitive behavioural therapy and mindfulness-based stress reduction — have good evidence behind them for chronic pelvic pain.
Non-hormonal medical options
- NSAIDs (e.g. ibuprofen, naproxen): Anti-inflammatory painkillers are often a first line for period pain. Timing matters — taking them before pain peaks can improve effectiveness.
- Nerve pain medications: Where central sensitisation is a significant factor, a doctor may consider medications that address nerve pain specifically.
Hormonal and surgical options
- Hormonal therapies: The combined pill, progestogen-only treatments, or a hormonal IUD can suppress the hormonal cycle that drives endometriosis activity, reducing symptoms for many women. A clinician will guide which is appropriate for your situation and fertility goals.
- GnRH analogues: These suppress oestrogen more significantly and are used in specific circumstances — a clinician will explain the implications, including add-back therapy to protect bone density.
- Excision surgery: For many women, surgical removal of endometriosis lesions — ideally by a specialist in a dedicated endometriosis centre — offers significant pain relief. The staging found at surgery will inform the surgical plan, but the decision to operate should rest on your symptoms and quality of life.
If you’re also managing the emotional weight of a chronic pain condition — the grief, the frustration, the impact on relationships and identity — that deserves support too. You can read more about the mental health impact of endometriosis and where to find support.
When to See a Doctor
Please seek medical advice if:
- Your pain is significantly impacting your daily life, work, or mental health at any stage of diagnosis.
- Your current treatment is no longer managing your symptoms adequately.
- You are experiencing new symptoms — such as pain during or after sex, bowel or bladder symptoms around your period, or pain outside your cycle.
- You are trying to conceive and have a known or suspected endometriosis diagnosis.
- You have never had a formal diagnosis but have had years of painful periods that have been dismissed.
You are entitled to ask for a referral to a specialist endometriosis service. In the UK, NICE recommends referral to a specialist endometriosis centre for complex or severe cases — but you don’t need to be Stage IV to deserve specialist care. If your quality of life is affected, that is reason enough.
Frequently Asked Questions
Can Stage I endometriosis cause severe pain?
Yes, absolutely. Stage I means minimal lesions by the rASRM scoring system — but if those lesions are near nerve tissue, or if central sensitisation has developed, pain can be severe. Research consistently shows no reliable correlation between staging and pain intensity. Your experience of pain is valid regardless of your stage.
Does Stage IV endometriosis always mean infertility?
Not necessarily, though Stage IV — particularly with significant adhesions or large endometriomas — does carry a higher risk of fertility challenges. Many women with Stage IV endometriosis conceive, with or without assistance. Fertility impact depends on the specific location and extent of disease, and a fertility specialist can give you a personalised picture.
Can endometriosis progress from one stage to another?
It can, but it doesn’t always. Endometriosis doesn’t follow a predictable progression — some women remain at the same stage for years; others see change. Hormonal treatment can suppress activity. Surgery can remove lesions. Staging is a snapshot at one point in time, not a fixed trajectory.
Why is endometriosis staged during surgery rather than through a scan?
Because most endometriosis lesions — particularly the superficial peritoneal type — are too small and flat to be reliably detected by ultrasound or MRI. Laparoscopy allows a surgeon to directly visualise and score the disease. Imaging can detect endometriomas and sometimes deep infiltrating disease, but a full staging picture requires surgery.
If staging doesn’t measure pain, what should I tell my doctor?
Describe your pain in terms of impact: days missed from work, activities you can’t do, sleep disruption, mental health effects. Use a pain diary if possible. You can explicitly say: “I know my stage is low, but my quality of life is significantly affected — I’d like to discuss treatment options that address my symptoms.” NICE guidelines support this approach.
This article is for general information and is not medical advice. It was reviewed by a certified healthcare professional in line with our editorial policy, and we update our content as the science evolves — but every woman’s body is different, so please speak to a qualified healthcare professional about your own symptoms.